A variety of automated liquid assay apparatuses for conducting assays of various liquids, especially biological fluids, for substances contained therein are known. Two such apparatuses are the TDx.RTM. Analyzer and ADx.TM. Analyzer available from Abbott Laboratories, Abbott Park, Ill. The TDx.RTM. and ADx.TM. analyzers are automated diagnostic assay instruments generally used to measure analyte concentrations in biological fluids such as serum, plasma, and whole blood. The ADx.TM. is specifically designed to conduct automated assays for drug of abuse analytes such as amphetamine/methamphetamine, cocaine, THC, morphine, heroin or the like. The TDx.RTM. analyzer has been previously described in other patents, commonly assigned herewith, such as U.S. Pat. No. 4,510,251 to Kirkemo et al.
The TDx.RTM. and ADx.TM. analyzers, for example, provide capabilities for both fluorescence polarization and nephelometric analysis, as well as for other systems of analysis. Whatever assay system is employed in a TDx.RTM. or ADx.TM. Analyzer, as in other instruments of the prior art, the assays are carried out by well-known techniques which involved dispensing reagents from bulk containers located remotely from the test samples undergoing analysis, mixing the reagents with the samples in reaction cuvettes while the latter are indexed, by means of a carrier, comprising a rotating carousel, or the like, from one analysis station to another. Subsequent to delivery of all reaction components to a cuvette, a wash or buffer solution is normally passed through the probe to eliminate any residual reaction components prior to subsequent tests. Typically, the wash solution is passed through the probe and dispensed to a remotely positioned waste container. While this internal cleansing of the probe is generally satisfactory, it does not provide for washing of the outer surface of the probe which can retain residual sample in certain assays.
Sample material retained on the probe surface is especially troublesome in automated analyzers where failure to adequately wash the outer surface of the dispensing probe can cause undesired sample carryover to subsequent tests. When the analyte or substance to be detected is a drug of abuse such as cocaine, THC, amphetamine/methamphetamine, morphine, heroin, or the like, preventing sample carryover is crucial to maintenance of sample integrity.
Accordingly, there is a need for an article which provides for effective washing or cleansing of the reaction component dispensing means of an automated liquid assay apparatus to eliminate the sample carryover and improve the performance of assays using readily available analytical instrumentation.